Various strategies for determining height clearance have been developed. An overhead clearance detection system and method may include a sensor for measuring a distance to an object. A vertical height for the object may be determined and compared to a user defined clearance height. If the object's vertical height is less than the user defined clearance height, an alarm may be sounded. The system may be removably mountable to a vehicle windshield.
Another approach uses a device for attaching directly to a high-profile and/or elongated item of cargo transported on the exterior payload area of a vehicle to prevent collisions with obstructions. A detector remotely detects a distant obstruction in the path of the cargo using ultrasonic, infra-red, or other sensing techniques. The detector is mounted directly to the cargo by a mounting member that releasably surrounds at least a portion of the cargo and provides an enveloping, frictionally constricting engagement to maintain the detector in a preferred operating orientation. The mounting member preferably includes a bracket configured to attach at multiple, spaced points on the cargo. In one alternative configuration, the mounting member comprises a flexible membrane which wraps around a portion of the cargo and is securely held in position thereto using tension straps. Alarm features include a light source and speaker contained in a passenger compartment and activated whenever the detector senses an obstruction in the path of the cargo. The detector and alarm components can communicate via an electrical cable, or using wireless transmission.